What is the purpose of toe-in/toe-out adjustments on the rudders?

• A. To adjust lift during takeoff.
• B. To adjust wing dihedral angle.
• C. To adjust stability based on angle of attack, with toe in at low AoA and toe out at high AoA.
• D. To switch between flight modes automatically.

Answer: (C)

Rudder toe-in/toe-out tuning is about shaping how the vertical tails respond to sideslip across the flight envelope. By adjusting the rudders so they have a slight toe-in at low angles of attack and a toe-out at high angles of attack, the airplane gets the right amount of stabilizing yaw moment where it’s most effective.

At low angles of attack, airflow is relatively clean over the tails, so toe-in increases the stabilizing yaw moment when the aircraft sideslips. This helps the airplane return to straight flight and stay tracking along the intended path, providing stronger directional stability during takeoff and cruise.

At high angles of attack, the flow over the tails becomes more disturbed and the tails are less effective. Toe-out moderates the stabilizing influence to avoid overcorrecting or inducing excessive yaw, which helps prevent issues like overcompensation or dutch roll while still maintaining good yaw control and coordination.

So, the adjustments tune directional stability and yaw damping across the flight regime, using toe-in for better stability at low AoA and toe-out to preserve controllability at high AoA.